1. Field
Example embodiments relate to gallium nitride (GaN) light emitting devices and methods of manufacturing the same. Other example embodiments relate to GaN-based light emitting devices on a silicon substrate and methods of manufacturing the same.
2. Description of the Related Art
Gallium nitride (GaN) and GaN-based nitride are widely used to form various electronic devices (e.g., power devices, light emitting devices or similar devices).
A GaN substrate is preferable for epitaxial growth of GaN-based material thereon. However, the GaN substrate is not appropriate when crystallinity, large-scale production and/or manufacturing costs are taken into consideration. A silicon carbide (SiC) substrate, or a sapphire substrate, is used to perform epitaxial growth of a GaN-based nitride. However, the SiC substrate is expensive, and the sapphire substrate may be bent due to low thermal conductivity when a semiconductor layer having a large diameter is grown on the sapphire substrate.
A silicon substrate is widely used for a GaN-based light emitting device. The silicon substrate is cheaper than the sapphire substrate or the SiC substrate. A silicon wafer having a large diameter of about 12″ may be used. Also, the silicon substrate has an electrical conductivity. As such, electrodes may be disposed on a lower surface of the silicon substrate. Thus, a process of manufacturing GaN devices may be easily performed. In addition, the silicon substrate has higher thermal conductivity than the thermal conductivity of the sapphire substrate. Thus, the silicon substrate is not easily bent when a GaN thin film is grown even at a high temperature.
However, due to a difference in lattice constants and in the thermal expansion coefficients between the silicon substrate and the GaN thin film, a dislocation density in the GaN thin film may increase and subsequently cracks may occur in the GaN thin film. In addition, the silicon substrate absorbs light generated in a light emitting layer. As such, an external quantum efficiency of the light emitting device is lowered.